Color television receiver chrominance control circuit



May 2, 1961 RHODES l-:r AL 2,982,812

COLOR TELEVISION RECEIVER CHROMINANCE CONTROL CIRCUIT Filed April 26, 1956 4 Sheets-Sheet 1 Ja PH @FEE/.sm

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COLOR TELEVISION RECEIVER CHROMINANCE CONTROL CIRCUIT Filed April 26. 1956 May 2, 1961 R. N.=RHoDEs rs1-AL 2,982,812

COLOR TELEVISION RECEIVER CHROMINANCE CONTROL CIRCUIT Filed April 26. 1956 4 Sheets-Sheet 4 IUST SEPHHTO'? @Il me 6I United safes PatentcoLoR'rELEvIsIoN REcEIvER CHROMINANCE l Y t coNrRoLCIRCUIT'v e j Roland N. Rhodes, Levttown Pa., and Joseph 0. Preisig,

Trenton, NJ.,` assignors to Radio Corporation of America, a corporation of vDelaware Filed Apr. 26, 1956, ser. No. 580,748 `1s Claims. (cl. vs -'5.4)

The present invention Yrelates to improved circuits for providing automatic .chroma control and color killer action, either singly or in combination, in a color-television receiver. l l

The television signal transmitted in commercial television broadcasting includes a monochrome informationr signal and picture deection signals. When the transmis- -sion is that relating to a color image, the television signal also includes a chrominance signal and colorr synchroniziing bursts. The chrominance signal contains color difference signals which aredemodulated by synchronousv demodulation. The color synchronizing bursts include reference phase information so that synchronous demodulating signals Acanbe developed at a point remote from the transmitter, such as at ya" receiver; the color synchronizing bursts are't'ransmitted on the back porch of the horizontalsynchronizing pulses.

A modern color television receiver may include either automatic chroma control circuits or color killer circuits or both. An automatic chroma control circuit maintains the amplitude of the chrominance signal in the chrominance channels of the receiver at a substantially constant level regardless `of uctuations `of the signal strength o fr y the television signal, information relating to burst am plitude is used for automatic chroma control. In order for automaticl chroma control and color killer circuits to be useful and effective in a modern television receiver, it is essential that theseicircuits be immune to noise and be positive actingrcircuits which require av m'inimurnV number of circuit componentsV so that the cost of manufacture of the color television receiver is not unduly increased. i v

Itis an object of the present invention to provide a simplilied and positive acting automatic chroma control and color killer circuit.

It lis another object` of this invention to provide an automatic chroma color killer circuit and an automatic chroma control circuit which performs at low signal level and under conditions of poor reception.

It is a still further object'of this invention to provideV a simpliiied means of developing a color killer control voltage and an automatic chroma control voltage in the burst-synchronized demodulating-signal source in a color television receiver. v

According to the invention, acontrol signal indicative of both the' presence or absence of the bursts and also of burst amplitude, when present, is developed by intro- 2,982,812` Patented May 2, 1961 `ice ducing a ringing' signal derived from each burst, when presentinto -an injection-locktype of oscillator circuitv whereupon the` phase of the oscillator oscillations are locked to'a phase prescribed by the burst and wherein a detected signal indicative of oscillator oscillation level combined with ringing signal level is developed by the mixing of the ringing signal and the phase-locked oscillator oscillations in an electron flow device of the oscillator to provide the aforementioned control voltage.

In one form of the invention, an oscillatory signal indicative of phase information relating to each colo'r synchronizing burst is introduced into a self-oscillating synchronous detector whose self-developed oscillations are' phase locked bythe voscillatory signal. The synchronous detection bythe phase-'locked oscillations of the applied oscillations produces a control voltage indicative of burst amplitude orof burst presence or absence. This controll voltage may be used to render a chrorninance Signal chanwhich, responsive to a filtered burst injected into an oscilnel amplifier inoperative when the bursts are absent and provide automatic chroma control of that channel when? the bursts are present.

kOther and incidental objects of this come apparent upon a reading ofthe following specification and a study of the drawings, wherein:`

Figures l, 2, 3 and 4 are diagrams ofvarious the present invention;

Figure 5 is a block diagram of a color television re' ceiver; Figures 6, 7 and 8 are the present invention.

'Figures l, 2 and 3 are circuits of the'present invention lator, develop therein a control voltage both indicative of the presence' or absence of the color synchronizing bursts "and offthe amplitude of each color synchronizing burst Ywhen present: i 'A .Y

- Figureflisf-aV circuit Villustratingo'ne form of the invention. A colortelevision signal and agate pulse 11V are `each applied toa burst separator 13 whose output is a separated burst.' The 'separated burst is thereupon passed'through a very narrow-band 3.58 mc. filter 15 to the control grid ofthe-tube 17. An oscillation developing circuit canbe coupled to the anode or to another grid'of the tube 17. The oscillation developing circuit l. 19, operating in conjunction withA the grid leak circuit 21 and the tube 17, develops oscillations in the electronA stream of tube 17. A typical though not definitive oscillation developing circuit 19 is included in Figure l; this circuit includesV a condenser 18 in parallel with an induc- .K tance 20. The condenser 18 and the inductance 20 are designed to resonate at the frequency of the bursts. The

cathode of'tube 17 is coupled to a tap on inductance 20 to provide a so-called electron coupledcircui connec-Y tion which causes oscillations to be developed in the electron stream of tube 17.

The filtered burst applied to the ycontrol grid of tube` 17 will vinjection lock these oscillations, The grid leak circuit 21 will cause the rectification of the sum of the phase locked oscillations and of the filtered burst developed between thecontrol grid and cathode of tube 17. Responsive to this rectification, Va continuous direct current voltage will be developed at the control grid and y therefore at the output terminal 27; this direct current voltage is indicative of both the presence or absence of the burst and also of the amplitude of the iiltered burst when the bursts are present. This direct current voltage may be employed as either an automatic chroma control voltage or ,a color .killer voltage or both. The direct current voltage, referred to as the automatic chromav .control and/or color killer control voltage developed at the terminal 27, is thereupon applied to the chrominance Y invention will be-y forms of schematic diagrams of forms of i channel 29 by way of a filter consisting of resistor 26 and a condenser 28 which smooths any iluctuations of the continuous voltage. The chrominance signal, termed chroma, is also applied to the chrominance channel-29. When the coloisynchronizing bursts are absent, the voltagey developed at the control grid of the ltube 17., will render the chrominance channel 29 inoperative so that no information appears at the output terminal 31. When the bursts are present, the 'automaticchroma control Voltage provided at the control grid of the tube 17 `will vary thev gain of the chrominance channel 29 Wherebythe amplitude level of the chroma at the output terminal 31 of that channel will be maintained substantially constantV regardless of uctuations irithey signal strength of the applied chroma. 2`

The phase-locked oscillations, introduced into the electron stream of tube 17 are developed across the output load 32. This signal produced across the output load 32 is ay 3.58 mc. signal which is, accurately phased to the phase prescribed by; the burst; this signal isuseable for color selection .in-'a color television receiver or monitor.

The circuitsof 'Figures 2 and 3 illustrate other metho'ds ofdeveloping automatic chromacontrol and'color killer voltages from an electron tube oscillator intowhose circuit a filtered burst is injected. 11n the circuit of FigureV 1 the iiltered burst from the 3.58 mc. filter 15'is applied tothe same control lgrid to which the oscillator feedback drive is also applied and to which a direct current voltage ,developing network such as the grid leak network 21 is coupled. The grid leak'network of Figure 1- includes thevresistor 25gand the condenser 23.

In the circuit of Figure 2, the iirst rcontrol grid is used inconjunctionV with the 'oscillation developing circuit for introducing oscillations into the electron stream of the tube 17. The-filtered Abursts 'are appled to `the second grid of tube `17. The filtered bursts on the second grid willcontrolrthe electron w to the iirst grid to cause injection locking `of the oscillations` developed by the os.

c illation developing circuit Vand-,develop the automatic chroma control and/or color killer control voltage at- The control grid and'cathode of triodel 17a are coupled to the` oscillation developing circuit 19 whichl develops oscillationsin the electron stream of the triode 17a. The variation of anode potential due tothe iiltered burst will cause phase-locking of these oscillations and rectiiication of the iiltered bursts and the phase locked oscillations at the control lgrid by the grid leak circuit will developra continuous direct current voltage in accordance with the invention. The automatic chrome control and/ or color killer voltage mayl actuallyrbe obtained either at the control grid terminal 33 or at the anode terminal 35 Vand applied therefrom to the chrominance channel 29. In the case of the circuit of Figure 3, the 3.58 mcfoutput wave is obtainable from the oscillation developing circuit 19.

v Figure 4 is a simplified block diagram illustrating one concept associated with the present invention. Consider first the action of a synchronous detector; a synchronous detector is a heterodyning device which heterodynes an intelligence bearing carrier with a synchronous demodulating Wave. Let a synchronous demodulating wave be developed by self oscillation within the synchonous detector and let this synchronousl demodulating carrier be phase-locked at a phase prescribed by the carrier ot thek intelligence bearing carrier. Upon introduction of the 4 carrier will be synchronously demodulated by the phaselocked oscillations developed therein to provide an output signal which is proportional in amplitude to the signal strength of the in-phase component of the intelligence bearing carrier and which is not -responsive to signal information in quadrature With the in-phase components of the intelligence bearing carrier. `Thus -it follows that the color killer and automatic chroma Vcontrol `circuit of the present invention is relatively noiseuininiuneV since much of the noise attendant. with, say, color Asynchronizing bursts in a television signal, isin the form of quadrature components; the output ofv the phase-locked oscillating synchronous detector is both a phase-locked 3.58 mc. outputrwave and a direct current control voltage having lan amplitude indicative-of the amplitude of the synchronizing wave.

`Before considering' detailedschernatic 'diagrams illustrating alternative forms of the present invention, vconsider the operation of the color television receiver Whose'block diagram is shown in FigureS. An incoming signal from a television broadcastl transmitter is received at the antenna 51 and applied to the television signal receiver 53.-

Y example, yan intercarrier sound circuit, the audio deteci chronizing signals from the television signal, and develops tor and amplifier .55 demodulatesthe sound signal, amplies the sound signal and applies the amplified sound signal to the loud speaker 57. y

lThe television signal is applied to the deection and high'voltage circuits 59 which separate the picture syntherefromhorizontal and vertical deection signals and a high' voltage. The vertical. and horizontal deflection signals are applied to. the ydeflection yoke 61; the high voltage is applied to the-ultor 63 of the color kinescope 65.V The deflection yandfhighY voltage ,circuits 59 also energize the gate pulsel generator `67 which-produces both a pulse `69 =of negative polarity at the terminal 70 and.

a pulse of positive polarity 71 at the terminal 68. The pulse' 71 has a time duration substantially in coincidence with the duration interval of the color synchronizing bursts. The Agate pulse generator 67 is vusually included in the color television receiver in the form of anl auxiliary winding on a high voltage transformer of the-deflection and high voltage circuits 59.

The television signal is applied byway `rif-terminal 72 to the chroma amplifier channel 73 which separates signals in the chrominance signal band from thetelevision signal-and applies signals in this band to the demodulator channel 75. This band is in the higherffrequenc'y The chroma amplifierV channel73 provides signals iny the chrominance signal range of 'the television signal to the burst separator 81 by Way Vof terminal'83. The burst separator` 8 1, responsive 'to the gate 'pulse 71 and to color synchronizing bursts, when present, provided from the chroma channel amplier 73, develops sepajrated color synchronizing bursts whichare thereupon applied 'to the burst synchronized oscillator and burst deintelligence bearing carrier into the phase-'locked oscilnal derived directlyfromthe'television signal receiver 53.'

The chr-oma'am'plier.

voltage will be applied at thel output terminal 89 and an automatic chroma control voltage will be applied at they output terminal 91.

When the bursts are absent thereby signifying monochrome transmission, the color killer 93, responsive to the gate pulse 69 andv'to the color killer control voltage4 from the burst synchronized oscillator and burst detector, will apply a biasing or color killer voltage to the terminal 77 of the chroma amplifier channel 73 to render this channel inoperative. When the bursts are present,

the voltage applied by the color killer 93 to the terminal 77 will not disable the transmission through the chroma amplifier channel 73. Concurrently, the burst synchronized oscillator and burst detector 85 will providev an automatic chroma controlvoltage to the terminal 79 of the chroma amplifier channel 73. The automatic chroma control voltage will vary inversely -with respect to the signal strength of the color synchronizing bursts in the television signal from the television signal receiver 53. The output of the chroma ampliiier channel 73, when the'bursts are present, will thereupon be a chrominance signalor chroma whose amplitude level is substantially constant and independent of fluctuations in amplitude level of the received chroma. Q

A reference signal from the burst synchronized ,detector 85 is applied'by way of terminal y87 to the phase shift circuits 97. The phase shift circuits provide selected phases of the reference signal to the demodulator channel 75, which, responsive to the chrominance signal from the chroma amplifier channel 73 by way of terminal 99, demodulates the R-Y, B-Y and G-Y color difference signals which are in turnapplied to corresponding control-electrodes lof the color kinescope 65.- p

Y The color television signal, which constitutes principally luminance information when not subjected to synchronous demodulation, is applied by Way of the Y delay line 101 and the Y amplifier 103 to the cathodes of the-color kinescope 65. Signal addition of the luminance or Y signal andeachv of the color difference signals provided by the demodulator channel 75, is performed within the color kinescope 65 to yield the televised image on the image face of that kinescope. It is to be appreciated that the aforementioned addition ofthe luminance signal and the various color difference signals can be alternatively performed in signal combining circuits separate from the color image reproducer With the resultant R, B

and G component color information signals applied to a color image reproducer. y

Figure 6 is a schematic diagram of one form'of circuit illustrating the chroma amplifier channel 73, the color killer 93, the burst separator 81 and the burst synchronized oscillator and burst detector 85 of Figure 5.

The chrominance signal is applied to the input terminal 83 and the ga-te pulse 71 is applied to the input terminal 68 of the burst separator 81. The resonant circuit 105 is resonant at the frequency of the burst. Responsive to the gate pulse 71 developed across the rectier 107, the control grid yof tube 109 is raised to a conduction level only during the duration of the gate pulse 71. The color synchronizing burst which occurs during the time interval of the Igate pulse 71, is'thereupon amplified t0 the anode of tube 109 and is developed across the resonant circuit 111 by Way of terminal 110. Consider at this point the detailed operation of the circuit of the present invention in Figure 6, namely, the burst synchronized oscillator and burst detector -85 of Figure 6. The separated color synchronizing burst from the Iburst separator 81 is developed across the resonant circuit'111 and lfrom there passed through the crystal lter 113 to the resonant circuit 115. One end of the resonant circuit 115 is connected to the control `grid of tube 117, and the other end is connected to the grid leak circuit 122. The output of tube 117 is connected to the resonant circuit 119 which is tuned towthefrequency o f the burst.

The resonant circuit 111to vvhich'the separated burst is applied includes an inductance 121.v A secondinductv ance'123 is coupled to the inductance 121; theY cathode of tube 117 is coupled by vvay of inductance 123 to 'a point of thereson-ant circuit 115, which is connected -to the control grid of tubel 117.V The circuit from, theA ,I cathode of tube 117 to the inductance 121 by Wayy of the inductance 123 constitutes ra feedback path of energy from' the cathode; the feedback energy is translated from inductance 121'through the crystal 113 and the resonant circuit k115 to the control grid of tube 117 so that oscillations will be develope-d in the electro-n stream of that tube. A grid leak circuit 122 and the center tap of inductance 123 are coupled to ground by way of the RC circuit 120. The RC circuit 120 is a balancing circuit which balances the residual negative bias voltage of the voscillator with a positive voltage drop produced by current from the cathode of tube 117 so that the voltage developed across resistor 131 of the grid leak 122 relative to ground potentialwill'be zero for the case when no burst is present.

The RC circuit 120 is termed the bias balancing RC circuit.

The resonant circuits 111 and 115 and the crystal filter 113 are resonant at the frequency of the separated burst. The oscillations ldeveloped by tube 1.17 are therefore at the frequency ofthe separated burst. The separated burstV is applied to the control grid of tube 117 by Way of the crystal filter 113; crystal filter 113, having a very narrow` taneously at the control grid lof tube 117. The combination of the ringing wave 4and the oscillator oscillationsV will be rectified between the cathode and first control grid of tube 117. This rectification will produce a bias voltage across the grid leak circuit 122. This bias voltage developed across the grid leak 122 is a direct current voltage Whose amplitude is proportional to the amplitude of the burst ringing wave, and therefore proportional to the amplitude of the burst and the signal strength of the chrominanoe signal. The g1id leak circuit 122 uses a resitsor 13-1 which has adjustable taps 133 and 135. Taps 133 and 135 are thereupon coupled to the output terminals 89 and 91.l A-t output terminal 89 a direct current,

control voltage, which is representative of the presence or absence of the burst, is provided; the control voltage will be at a maximum negative value when the bursts are absent. When the bursts are present, the bias voltage across the grid leak 122 will be negative and proportional to the burst amplitude; for maximum burst during phase synchronism, the bias voltage will be at its most negative value.V The control Voltage developed at the output terminal 89 may therefore be used as a color killer control voltage. l

The tap 135 ofthe grid leak 122 is coupled to provide a control voltage to the output terminal 91. This control voltage is used as an automatic chroma control voltage or A.C.C. voltage which varies with burst amplitude.

A 3.58 mc. wave which is phase-locked by the burst when present, is developed across the resonant circuit 119 and developed at .the output terminal 87 of the, burst synchronized oscillator and burst detector 85.

In the form of the burst synchronized oscillator and 'l control grid of rtube 117. This provides additional stability forthe operation of the Yoscillation developing 'mechanism of the burst synchronized oscillator and burst detector 85. In addition, the condenser 124 translates 180 out-of-phase separated burst information, relative to the phase of burst information passing through the crystal 11310 terminal 125. The crystal 113 has shunt capacity derived principally from the crystal holder. .The 180 out-of-phase'separated burst infomation at terminal 125 will thereupon neutralize burst sidebands passing through the shunt capacity.

The operation of the burst synchronized oscillator and burst detector 85 may also be interpreted in terms of synchronous detecter action. Both the burst-phase locked oscillations by the oscillation developing circuits and the burst Vringing Wave are developed at the first control grid of tube 117. Synchronous detection of these waves combined at this lirst control grid, will take place utilizing the rectication between fthe first control grid and cathode to provide the voltage `across the grid leak circuit 122 which is proportional to the results of this synchronous detection and rectication. As has been mentioned previously in connection with other figures of this application, since noise components accompanying even the burst ringing wave include quadrature components, these quadrature components will be eliminated by the synchronous detection action which is 'only responsive to in-prhase signals. This feature causes the circuit of the present invention to be substantially noise immune.

The chroma amplier channel 73 of Figure 6 uses the tubes 141 and 143 connected in cascade. An applied colo-r television signal is filtered by ythe input filter circuit 145 which includes the 4.5 mc. sound trap 147 and the reso-` nant circuit 149 which is suciently broadband to apply the entire chrominance signal at the control grid of` tube 141. A bias voltage point 151 is coupled to the control grid of tube 141. The magnitude of any bias voltage applied at that point will control the gain of tube 141. Tube 141 drives the transformer 153 which in turn drives the control grid of tube`143. The output stage of tube 143 is the circuit 155 across which the amp-lined chrominance signal is developed. This amplified chrominance signal is thereupon developed latroutput terminal 99, from which terminal it is -applied to the demodulator channel 75. In the form of chroma amplifier channel 73 shown in Figure 6, the chrominance signal andthe color synchronizing bursts `are coupled from the output of transformer 153 to the input terminal 83 of the burst separator S1. In this way the burst is amplified in tube 141 before the separation of the `burst from the chrornin-ance signal by the burst separator 81. It is to be appreciated that the amplified burst can also be derived from the cathode or anode of tube 143. The point of burst takeoif from tube 143 will 'actually depend upon whether or not burst energy is required for the burst separation; in the case of a diode gate circuit, burst energy is usedto laid in the gating process.

l 'I'he automatic chroma control voltage (A.C.C.) delivered to terminal 91 by the burst synchronized oscillator and burst detector 85 is applied to the bias terminal 151 of tube 141 by way of terminal 79. This A.C.C. voltage developed at bias terminal 151 controls the gain of the tube 141 in which both the chrominance signal and burst are amplified. The gain is so controlled by the automatic chroma control voltage that the amplitude level ofthe burst and chrominance signal produced at the transformer 153 is substantially independent of iiuctuations in the signal strength of the chrominance signal region of the color television signal.

'Ilhe color killer 93, embodying a preferred, but not necessarily delinitive color killer circuit, is dagrammed in detail in Figure -6. .The color-'killer control voltage delivered to terminal 89`by the iburst synchronized oscillator and burst detector is applied'tothe control gn'd of tube 1610iy Vthe color, killer 93. This ycolor :killer controlvoltage* is .at its least negative value when theA bursts are absent, and at a morenegative value when the bursts are present-this more negative value being dependent in actual magnitudeupon the amplitude of the burst.

Whenl the bursts are absent the tube 161 of the colorv killer 93 is biased to be capable of conduction responsive to signals applied to its control grid. Pulses 69 are applied to the control grid of, tube 161 by way of terminal 70. 'Ihese pulses 69, of negative polarity, pulse In this way the chroma amplifier channel 73 will notv be permanentlyrendered inoperative by monochrome transmission inasmuch as the takeoff point -for the burst vis after the gain control point of that channel.

When the pulses 69a have causedY tube 141 to conduct duringV burst time and when no bursts have passed through that tube, a lcombination of bias voltages will be producedy at the bias terminal 151; thisV combination Vof bias voltages includes` the automatic chroma control voltage and a voltager developed across theiresistance and condenser .parameters inthe gridy circuit kof tube 141 due to the current drawn to the control grid of tube 141 by pulses 69a. Thiscornbination ofbias voltages will cause tube 141 to be biased beyond cutolf until the next pulse 69a.

yWhenrthe bursts are present the color killer control voltage biases the tube 161 of colorrkiller 93 beyond cutoi. No pulses are produced at the bias terminal 151 in response to pulses 69. Tube 141 conducts atall times and its gain is dependent upon the magnitude of` the automatic chroma control voltage provided by wayl of terminal 91 from the burst synchronizedy oscillator and burst detector 85. p

Figure `7 is a schematic diagram of the burst separator 81 of Figure 6.and of a burst synchronized oscillator and burst detector 85 which embodies another form of the present invention. The separated burst from` the burst separator 81 is applied by way of the anode terminal to a tuned resonant circuit 171 across which circuit the separated burst is developed. 'I'he tank circuit 173 of the burst synchronizedoscillator and burst detector 85 includes the tuned resonant circuit 171 and the parallel resonant circuit 185 and involves a coupling circuit 180 having unusual characteristics. This coupling circuit 180 includes the crystal 175 coupled from the inductance 177 of the tuned resonant circuit 171 to the point 183 connected to the resonant circuit 18S; the crystal isin series with the vcondenser 179. The crystal 175 and the condenser 179 are series resonant at the frequency of they burst and have the property of ltering the separated burst as the separated burst is translated to the point 183. The condenser 181 is coupled between point 183 and the end of winding 177 to developrat point 183 separated burst information which is out-of-phase with separated burst information passing through the crystal 175. This out-of-phase separated burst information, translated' to point 183, neutralizes any burst sidebands passing through the crystal shunt capacitance. Since the crystal 17'5 is operated at series resonance, yit will exhibit minimum attenuation atgthel` frequency of the burst thereby providing minimum attenuation of the burst as it Vpasses through the crystal.

Theresonant circuit 185 is coupled to the control grid of tube 117 by way of the grid leakl circuit 187 and to groundby way of the bias-balancing'iRC. circuit 119a. The cathodeof tube 117 is connected to a tap of the inductance 177 with the coupled-to-ground side of the resonant circuit 18S also coupled to a tap of inductance 177. f By proper choice of the position of these taps on the inductance 177, oscillations will be developed in the tank circuit 173 and in the electron stream of tube 117. Oscillations developed in the electron stream of tube 117 will thereupon be developed in the output circuit 119 and caused to be presented at the outputterminal 87.

` 'Ihe signals developed at the control grid of tube 117 include both the oscillator oscillationspresented there a'` control voltage which is proportional to the amplitude of the burst when present and 'which will also indicatei the` absence of the'burst during monochrome transmission. This control voltage developed is further integrated by an integrating or lter circuit consistingof the resistor 191 and the condenser 193 and is therefrom presented at the terminals 489 and 91 to be used for color killer control and automatic ,chroma control in a manner described in connection with Figure 6.

In the burst separator 81 of Figure 8, the chroma and burst are appliedby way of terminal 83 to the transformer 201 which is responsive to the frequency band normally occupied by the chrominance signal and the burst. Theresonant circuit 201 is connected to the rectifier 203. The gate pulses 71 are coupled from terminal 68 by way of a resistance condenser network, including the condenser 205, the-resistance 207, the condenserv 209` and the resistance 211, to the terminal of'v the rectifier 203 to which the o'utputrof the transformer 201 isalso applied. During the gate pulse 711the'rec-` tifi'er, 203 iscaused to conduct thereby passing the burst, Y

which 'occurs during the-interval of the gate pulse 71, to the, inductance 177. .During ,intervals between the gateV pulses 71 the aforementioned resistance condenser network, responsive torectiiication of the gate pulse, 71"bythe `rectier- 203, develops a voltage at the-recincludes the crystal 175,; andthe condensers 179 and 181;

condenser 181 is a neutralizing condenser. As` inthe case of the. corresponding circuitof Figure 7, the series resonant loop 180 of Figure 8 filters the burst and develops the tilteredburst. in the `form of acontinuousV ringingy signal at the terminal183. Terminal 183 is coupled to the control. gridfof tube 213 which functions as an ampliiier tube. VResistors 215 and 217 provide proper loading ofthe crystal 175. The cathode-to-grid capacitance 219 may be considered as a part of the series resonant loop 180.v

The filtered burst whichvis applied to the control grid'- grid of the' oscillator tube '117. The cathode of tubey 11`7 is inductively coupled to the anode inductancev 221 by way of the coupling loop 225 in a manner whereby oscillations are developed in both the anode inductance 10 221` and alsoin the electron stream of tube 117. Both the control grid of tube 117 and the ott-cathode terminal of the coupling loop 225 are connected to the bias balancing RC circuit 227. trolfgrid of tube 117 .will thereupon bea combination of both the oscillations developed by oscillator action in the anode inductance 221 and the iiltered burst which isdeveloped there by way of amplifier tube 213; theA coupling condenser 223 prevents the anode voltage of tube' 213 from being applied to the control grid of tube-117. The -ltered burst,when present, will also phase-lock theoscillations; rectification between cathode and grid of tube 117 of the iiltered burst and of the phase-locked oscillations will developvat the grid terminal. 189 a control voltage which is proportional to theamplitude of the.

iiltered burst when presentand which is indicative of the absence of any bursts as in the caseof monochrome trans-- mission. The control voltage at the grid terminal 189 is thereupon integrated by fthe filter-circuit comprising the resistor 191 and the` condenser 193 and developed a continuous direct current voltage at theoutput termi-f nals 89 and 91 for use as a color killer control voltagel and an automatic chroma control voltage. I'he phase locked oscillations developed in the electron stream of tube 117iare developed across the outputload 119 andtherefrom at the output 'terminal 87.

The circuit of *Figure` 8l may be alternatively `connected whereby a feedback signal m-ay be derived from a tube element of tube 117 and applied to the circuit 180 so that oscillations will be jdeveloped through both the crystal 175 and the anode inductance 221; crystal 175 will thereupon also -iilter the oscillator feedback energy thereby rendering the oscillator action more' stable.

Having described the invention, what is claimed is:

l. In a color television receiver adapted to receive a television signal, V.said television'signal including intermittent colorsynchronizing bursts consisting of oscillatory information during prescribed time intervals' and having. aprescribed phase and frequency and occurring only,dur-.

ingcolor transmission, the combination` of: an oscillatorto develop`4 arroscillatory` signalV which is phase-locked during colortransmission to the frequency and phase of information channel coupledfto said oscillator for processing signal information 'in a selected higher frequency range ofsaid television signal; and means for applying said. controlY voltage tov said color information channel to control the amplitcation of said` colorinformation channel.V v

`2L In a color television receiver adapted to receive a television signal, said television signal including intermittent color synchronizing bursts -having a prescribed phase and frequency only during color transmission, the combination of; an oscillation developing circuit including anv electron ow device yhaving an'electron flow into which oscillations are introduced'to be amplified-and therefrom v caused to produce sustained oscillations; means to develop during color transmission an oscillatory signal yfrom saidbursts; means coupled to saidV electron ilow devices for applying said oscillatory signal `to said electron flow;'

detection means coupled to theoutput of said oscillatory signal developing circuit fordeveloping a control signal indicative ofthe presence or absence of said `bursts and of thev amplitude ,of vsaid bursts when present; a color information channel 4for processing signal information in Va selected higher frequency portion of the frequency range of saidftelevision signal; and means for applying said control signal to said color information channel to render said 'Ille signals developed at the 'conlI formation channel according, to the amplitude of saidbursts during color transmission.

3,. Ini a color television receiver adapted to receive a. television` signal, said, television signal includingk intermittent vcolor synchronizing bursts having a prescribed phase and frequency only during color transmission, the combination of: an oscillation' developing circuit including an electronilow' devicevhaving an electron ow and. includinglmeans to introduce oscillations into said electron. ow toA be amplified and therefrom caused to produce sustained oscillationsgrmeans to develop during color transmission an oscillatory signal fromY said bursts, said oscillatory signal being continuous at least during each scanning aline; said oscillation introducing means including. means to introduce' modulations representative of said oscillatory signal into said electron flow to phase lock. said sustained oscillations; detection means in said oscillatory circuitl coupled to said electron flow-device toA developfa control signal indicative of the presence or the absence of said. vbursts` and` of the amplitude of said burstsv when present; a `color information channel for processing signal information in a selected higher frequency portion of the frequencyV range of said television signal; and means for applying said control signal to said color information channel to render said color information channel inoperative when said bursts are not present.

4. In a color television receiver adapted to receive-l a color television signal, said television signal including a chrominance signal and color synchronizing bursts in a higher frequency range of said television signal only during color transmission, said color synchronizing bursts occupying, when occurring, a prescribed time interval during each retrace interval, the combination of: an oscillator circuit having arl" electron flow device and a p'oint at which oscillator feedback energy is introduced into the electron ow of said electron ilow device to be amplied and 'cause the'k development of sustained oscillations; means for developing a' continuous oscillatory signal having a frequency Vand phase and amplitude prescribed by said bursts when' said bursts are present; means `for impressing said` bursts upon said oscillatory signal developing means; means toapply said oscillatory signal at said point of application of feedback energy in said electron flow device `to cause said sustained oscillations to be phase-synchronizedaccording to the phase of said oscillatory signal and to develop at that point areference voltageindicative of the amplitude of said color synchronizing Vburstsvduring lcolor transmission and of transmission other than color transmission when said bursts are not present; a chrominance channel for processing andv amplifying chrominance signal information inl said higher frequency range of said television signal normally-occupied by said chrominance signal during color transmission; means for impressing said higher frequency range of said televisionV signal upon said chrominance channel; and means to apply said control voltage to said chrominance channel to render inoperative said chrominance channel when said bursts are absent and to vary the gain of said chrominance channel according to a prescribed relationship with respect to the amplitude -of said bursts during said color transmission.

'5. ln a color television receiver adapted to receive a television signal, said television signal-including a chrominance signal and color synchronizing bursts in a higher frequency range of saidV televisionY signal only during color transmission, said'color lsynchronizing bursts ocand phase and amplitude prescribed by said Aburstswhen saidbursts are present; means for. impressing saidv bursts upon said oscillatory signal developing means; means .to

pass said oscillatory signal throughisaid resonant circuiti to said point of application of feedback energy infsaid electron'ow device to cause said` sustained. oscillations to be phase-synchronized according to the phase of said.` oscillatory signal; grid-leak means'to develop `at saidl point of application of feedback energyea' reference volt-- age indicative of the presence or absence of said bursts and of the amplitude of said bursts when present; a

chrominance channel for processing and` amplifying.

chrominance signalinformation in said higher frequency range. of .said television signal normally occupied by said chrominance signal during color transmission; means for impressing said higher frequency range of said television signal upon said chrominance channel;

and means to apply 'said reference voltageto said chromif' nance channel to render inoperative saidl chrominance channel when said bursts are f absent and` to vary the gain of saidchrominance channel accordingto a prescribed relationship with respect to the amplitude of'V during color transmission, said color synchronizing bursts a occupying, When occurring, a prescribed time interval during each retrace interval, the combination of: an electron tube having an anode, control grid and a cathode; an oscillation output circuit coupled between saidl anode and cathode; a tank circuit resonant at the frequency of said bursts and coupled to at least said concupying, when occurring, a prescribed time interval durf trol grid and cathode to develop oscillations and to present feedback oscillations at said control grid fromV said oscillationoutput circuit; means including said tank circuit to filter said bursts during color transmission to' develop a ringing signal having a frequency and' phase prescribed by said bursts and to apply said ringing signal to' said control grid to both phase-synchronize said oscillations and to cause the rectification of both said" ringing signal and said feedback oscillations to develop a control voltage indicative of the presence or absence of'saidbursts and of the amplitude of said bursts during color transmission; a chrominance channel for' processing and amplifying signal information in sai'd higher' frequency range of said television signal normally occupied by said chrominance signal during color transmission; means for impressing said4 higher frequency range ofsaid television signal upon said chrominance channel; and means to apply said control voltage to said chrominance channel to render said chrominance amplifier inoperative when said bursts are absent and to vary the gain of said chrominanceY amplifier in prescribed relationship to the amplitude of said bursts during color transmission.

7. Ina color television receiver adapted to receive a color television signal, said television signal including a chrominance signal and color synchronizing bursts in a higher frequency ranger of said television signal only dur# ing color transmission, said color synchronizingbursts occupying, whenoccurring, a prescribed timeinterval during each retrace interval, the combination of: an electron tube having an anode, control grid and a cathode; an oscillation output circuitcoupled between said anode and cathode; a tank circuit resonant at the frequency of said bursts and coupled to at least said control grid and cathode to develop oscillations and to present feedback oscillations at said control gridrfrom said oscillation output circuit; means including said tank circuit to filter said bursts during color transmission to develop a ringing signalY having a frequency andv phase prescribed by said bursts and to apply said ringing signal to said control grid to both phase-synchronize said oscillations and to 13` cause the rectification of both said ringing signal and said feedback oscillations to develop a control voltage indicative of both the amplitude of said bursts during color transmission and also of transmission other than color transmission as indicated by the absence of said bursts;.a chrominance channel for processing and amplifying signal information in said higher frequency range of said television signal normally occupied by said chrominance signal during color transmission; means for impressing said higher frequency range of said television signal upon said chrominance channel; means to apply said control Voltage to said chrominance channel to vary the gain of said chrominance ychannel according to a prescribed relationship to the amplitude of' said bursts during color transmission; an electron discharge'device operable for providing anelectron vdischarge during each retrace interval; means for pulsing said electron discharge device to render it operative; means to apply said control chrominance signal and color synchronizing bursts in a higher frequency range of said'vtelevision signal only during color transmission, said color synchronizing bursts occupying, 'when occurring, a prescribed time interval during each'retrace interval, 'the combination of: an

bursts; means including a grid leak circuit to couple said voltage to said electron discharge device to render said occupying, when occurring, a prescribed time intervalv during each retrace interval, the combination of: an electron tube having an anode, control grid and a cathode; an oscillation output circuit coupled between saidtanode and cathode; a tank circuit resonant at the frequencyof .said bursts and coupled to at least said control grid and cathode to develop oscillations and to present feedback oscillations at said control grid from said oscillation output circuit; means including said tank circuit to filter said bursts during color transmission to develop a ringing signal having a frequency and phase prescribed by said bursts and to apply said ringing signal to said control grid to both phase-synchronize said oscillations and to cause the rectification of both said ringing signal and said feedback oscillations to develop a control voltage indica- A tive of both the amplitude of said bursts during color transmission and also of transmission other than color transmission as indicated by the absence of said bursts; a chrominance channel for processing and amplifying signal information in said higher frequency range of said television signal normally occupied by said chrominance signal during color transmission; means for impressing said high frequency range of said television signal upon said chrominance channel; means to apply said control voltage to said chrominance channel tol vary the gain of said chrominance channel according to a prescribed relationship to the amplitude of said bursts during color transmission; an electron discharge device operable for providing an electron discharge during each retrace interval; means for pulsing said electron discharge device to render it operative; means to apply said control voltage to said electron discharge device to render said device inoperative during color transmission when said bursts are present and to render said device operative when said bursts are absent; and means responsive to the pulsing of said electron discharge device to render said chrominance signal channel inoperative and to render said channel inoperative between said time intervals normally occupied by said bursts and to render said chrominance signal channel operative during said time intervals normally occupied by said bursts when said bursts are absent.

9. In a color television receiver adapted to receive a color television signal, said television signal including a tank circuit tosaid control grid and cathode to develop oscillations andL to presentfeedback oscillations at said control grid from said oscillationoutput circuit; means to filter said bursts during color transmission using said tank circuit todevelop a ringing signal having a frequency and phase prescribedv by said bursts andto applyf saidY ringing signal'tovsaid cont-rol grid to both phasesynchronize said oscillations and to cause the Arectification of both said ringing signal and said feedback oscillations to develop a control voltage indicative of both the amplitude of said bursts during color transmission and also of transmission other than color transmission as indicatedby thel absence of said bursts across said grid leak circuit; a chrominance signal channel for processing and amplifying signal information in said higher frequencyrange of said television signal normally occupiedby said chrominance signalduring color transmission; means for impressing said high frequency range of said television signal upon said 'chrominance channel; and means to apply said control voltage to said chrominance signal channelto render said chrominance signal channel` inoperative when said bursts are absent and to vary the gain of said chrominance signal channel in prescribed relationship to the amplitude of said bursts during color transmission.

10. Ina color television receiver adapted to receive a television signal, said television signal including intermittent color synchronizing bursts having al prescribed phase and frequency only during color transmission, the combination of: an oscillation developing circuit including an electron flow device having an electron llow and a grid leak circuit coupled to a point of said electron flow into which oscillations are introduced to be amplified by said electron llow and therefrom caused to produce sustained oscillations; means to develop during color transmission an oscillatory signal from said bursts, said oscillatory signal continuous at least during each scanning line; means to apply modulations representative of said oscillatory signal into said grid leak circuit to phase-lock said sustained oscillations and to develop a control signal indicative of the presence or absence of said bursts and also of Ithe amplitude of said bursts when present; a color information channel for processing and amplifying signal information in a selected higher frequency portion of the frequency range of said television signal; means for impressing said higher frequency range of said television signals upon said color information channel; and means for applying said control signal to said color information channel to render said color information channel inoperative when said bursts are not present and to control the gain of said color information channel according to the amplitude of said bursts during color transmission.

11. In a color television receiver adaptedto receive a television signal, said television signal including intermittent color synchronizingbursts having a prescribed phase and frequency only during `color transmission, the combination of: an oscillation developing circuit including an electron ow device having an electron ow into which oscillations are introduced to be amplified and therefrom caused to produce sustained oscillations; means to develop during color transmission an oscillatory signal from said bursts; means to introduce said oscillatory aasasiz'" signal into said electron 110W; detection means traversed by at least a portion of the electron flow in said electron diow device to develop a control signal indicative of the presence or absence of said bursts; a color information channel for processing and amplifying signal information in a selected higher frequency portion of the frequency range of said television signal; means for impressing said' higher frequency range of said television signal upon said color information channel; and means for applying said control signal to said color information channel to control the gain of said color information channel according to the amplitudey of said bursts during color transmission.

l2. In a color television receiver adapted to receive a television signal, said television signal including intermittent color synchronizing bursts having a prescribed phase and frequency only during color transmission, the combination of: an oscillation developing circuit includying an velectron ow device having an electron flow and duce-sustained oscillations; means to develop during lcolorV transmission an oscillatory'signal fromV saidv bursts, said oscillatory signal continuous at least during each scanning line; said oscillation introducing means including means to introduce modulations representative of said oscillatory signal intosaid electron flov'v to phase-lock said sustainedY oscillations and also detection means traversed by at least a portion of the electron ilow in said electron flow device to dev elop a control signal indicative of the 'presence or the absence of said bursts and of the amplitude of said bursts when present; a color information channel for processing and amplifying signal information in a selected higher frequency portion of the frequency range of said television signal; means for impressing said higher frequency range of said television signal uponsaid color information channel; and means for applying said coni6 trolv signal to said color information'channel to`render said color information channel inoperative vvhen said: bursts are not present and to control the gain'of saidl color information channel according to the amplitude of y output signal having a predetermined phase relationship'` to said bursty signal, synchronous detector means in s aid. oscillator jcircnit to develop a direct current control volt-l age of an amplitude related to the amplitude of said burst signal, andy means for applying said control voltage to said chrominance amplifier to control the vgain thereof in accordance with the Vamplitude of said burst signal.l

i References Cited in the le of thisipatent v.UNlTED STATES PATENTS 2,681,379 Schroeder .Tune l5, 1954 2,740,046 Tellier Mar. 27,` k1956 2,757,229 Larky July 3'1, ,195.6y 2,776,334 Goldberg Jan. 1 1957 Flood et al. May 20, 1958y OTHER REFERENCES RCA Lnfsii, Fig. 5, page 5,-Dec. 5, o. Introduction to` ,Color TV, Kaufman and Thomas,

I. F. Rider Publisher, Inc.; copyright 1954; G. E. circuity facing inside back cover. j

Circuit Diagram RCA Model Z1-CT-7835, Service Data, 1956, T5. 

